WNAC 1200

Dan.Strassberg dan.strassberg@att.net
Thu Aug 2 06:26:34 EDT 2012

The range of AM signals is inversely proportional to their frequency. 1260
is almost two times 680, so if the power of the 680 and 1260 stations were
equal and they both transmitted from the same antenna (neither of which is
the case), the 680 station's signal would cover four times the area covered
by the 1260 station's signal. (Well, not exactly: in terms of wavelengths, a
given tower is almost twice as high at 1260 as it is at 680, and within
limits, an electrically taller tower is more efficient than an electrically
shorter one. So you could say that if two stations, one at 680 and one at
1260, broadcast from the same tower, you should compare the range of the
1260 station running 5 kW with the range of a 680 station running 10 kW. In
THAT comparison, the 680 station's signal would cover four times the area
covered by the 1260 station's signal. It isn't quite that straightforward,
several other issues are involved--particularly, soil conductivity and
directional patterns--but that should give you the idea. One other point:
Except under unusual circumstances, doubling power does NOT double the area
covered; the effect is generally much less dramatic.

As for Sheppard's proposed 50-kW station on 1200, it would also have been
better than his 1260 station not only because he was proposing ten times the
power on 1200 as he had on 1260, but also because there was very little
interference from other stations on 1200 and quite a bit of interference on
1260. That effect is probably much less dramatic today then it was in 1940.
In 1940, there was only one station in North America on 1200 and a perhaps
dozen on 1260. The 1200 station, in San Antonio TX, was almost 2000 miles
from Boston. In 1940, the 1260 station that was closest to Boston was in
Washington DC. Today, there are dozens of stations on both 1200 and 1260.

Dan Strassberg (dan.strassberg@att.net)
eFax 1-707-215-6367

----- Original Message ----- 
From: "A Joseph Ross" <joe@attorneyross.com>
To: <boston-radio-interest@lists.BostonRadio.org>
Sent: Wednesday, August 01, 2012 11:57 PM
Subject: Re: WNAC 1200

> I understand why 680 was much better, but.maybe people out there could
> indulge this non-engineer a bit more and explain why was 1260 that bad and
> why would 1200 have been that much better?
> -- 
> A. Joseph Ross, J.D.|92 State Street|Suite 700|Boston, MA 02109-2004
> 617.367.0468|Fx:617.507.7856|http://www.attorneyross.com

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